The invention relates to a method for parameterizing a software damper connected to a clutch control system for damping chatter vibrations of a clutch torque being transferred by means of an automated friction clutch which is controlled by the clutch control system by means of a target clutch torque and which is positioned between a combustion engine and a drivetrain of a motor vehicle, wherein the target clutch torque affected in specified operating states by chatter vibrations is corrected by means of the software damper, wherein a transfer behavior of a clutch torque transferred via the friction clutch on the basis of the target clutch torque is ascertained during a modulation of the target clutch torque and the software damper is parameterized with the help of the ascertained transfer behavior.
Automated friction clutches, for example friction clutches combined into a dual clutch, are sufficiently well known and are inserted into drivetrains having a combustion engine and a transmission, for example an automated shift transmission, dual-clutch transmission or the like, between the combustion engine and the transmission. The friction clutch is operated in such cases by means of a clutch positioner as well as a clutch actuator. The clutch actuator is controlled by a clutch control system. The clutch control system contains a regulator that operates the friction clutch on the basis of a target clutch torque which can be obtained by means of a driving strategy program for example depending on a driver's desired torque, driving situations, road conditions and the like, in such a way that a specified clutch torque is present at its output.
Because of the properties of the friction clutch, the transmission and the like, chatter processes may occur at the friction clutch which result in a vibration-accompanied transfer of the target clutch torque with a fixed frequency response in a frequency range up to 30 Hz for example.
In order to attenuate this frequency response, a method for reducing chatter vibrations is known from DE 10 2013 204 698 A1, in which an emulated vibration absorber, i.e., a software-based vibration absorber, is superimposed on the clutch positioner for the target clutch torque as a software damper.
Knowledge of the drivetrain behavior and of the transfer behavior on the basis of the target clutch torque is necessary for system identification and design. In order to ascertain this transfer behavior, chatter vibrations are simulated by modulating the target clutch torque and drawing upon the resulting signals which are relevant for driving comfort, for example the longitudinal acceleration of the motor vehicle or the transmission input speed, to design and parameterize the software damper, for example a regulator or filter.
This purpose is served by modulations of the target clutch torque in the relevant frequency range of chatter vibrations, typically between 2 Hz and 30 Hz. Here, a frequency response of the system is determined, for example over a control link beginning with the clutch control system, through the clutch positioner, through the friction clutch subject to chatter vibrations to its output, for example a transmission input shaft vibrationally coupled, by carrying out for time periods of typically a few seconds a sinusoidal excitation having a fixed frequency in the desired operating state on the clutch torque for example with a step width of 0.5 Hz across the relevant frequency range of the chatter vibrations in relevant operating states, for example moving off and creeping situations and when engaging the clutch after gear changes. The evaluation of the transfer behavior is carried out largely by hand, by relating the amplitudes of modulation torque and transmission input speed or longitudinal acceleration to each other in a component-by-component examination of the frequency components according to a discrete Fourier transformation. This yields a transfer function which is used for parameterizing the software damper. This method is very time-intensive.